The invention relates to a drive for switching a double seat valve, more particularly a double seat valve capable of seat cleaning, having two closing elements that are movable independently of each other, which enclose a leakage cavity between themselves that is connected to the surrounding area of the double seat valve, wherein the first closing element after a partial stroke comes into abutment on the second closing element and this with the further opening movement thereof also transfers into an open position, with adjusting rods for the closing elements arranged concentrically in each other, which are guided from a valve housing outward into and out of the drive and via which the closing elements, in addition to the open position, can each be brought selectively and independently of each other into a partially open position, wherein the open position is generated by a main adjusting arrangement and the partially open positions are generated by the individual adjusting arrangements assigned to the respective closing element, and the individual adjusting arrangements are arranged on the one hand between the main adjusting arrangement and the valve housing and on the other hand are arranged together with the main adjusting arrangement in a common housing of the drive, having a first drive piston of the main adjusting arrangement that engages in the direction of the associated open position at the first adjusting rod for the first closing element against the force of a first spring, and having a third drive piston of the second individual adjusting arrangement for the second closing element, which can be brought in engagement in the direction of the associated second partial opening in driving connection with a second adjusting rod of the second closing element, wherein the first drive piston on the side thereof facing the valve housing is delimiting a first pressure medium chamber for generating the fully open position, and on the side of the third drive piston facing away from the first pressure medium chamber has a third pressure medium chamber for generating the second partial opening.
A generic drive for closing a double seat valve is known from the document EP 1 725 795 B1. This drive supplied with pressurizing medium which is formed as a spring-piston drive, can be inserted in two configurations, and specifically in a first configuration that is suitable for actuating a double seat valve capable of seat cleaning, having a first closing element formed as a slide piston and a second closing element formed as a seat plate. The second configuration is suited for actuating a double seat valve capable of seat cleaning having two closing elements formed as seat plates. With the first configuration, the two partially open positions are oriented in opposing directions, and with the second configuration the two partially open positions are oriented in the same direction. With both configurations, the completely open position and the second partially open position of the second closing element have the same orientation. Both configurations are formed having identical structural components, wherein in both configurations the first partial opening of the first closing element is generated respectively by a spreading movement of the first and the second drive pistons. With the first configuration, the first drive piston is arranged limited axially movable on the first adjusting rod, and the second drive piston is fixed immovably on the first adjusting rod. With the second configuration, the arrangement relationship of the two drive pistons on the first adjusting rod is reversed. The first drive piston of a main adjusting arrangement is moved against the force of a spring for the completely open position, wherein this spring is arranged on the side of the first drive piston facing away from the valve housing. Due to this arrangement of the spring, the drive is extended by an additionally needed axial construction space, which is due to accommodating the pretensioned spring, in the direction of fully opened stroke performed therein via the first drive piston.
With a drive for a double seat valve capable of seat cleaning described in the document EP 0 866 934 B1, that is only suitable for the second configuration of the drive described above, the spring, against which the drive piston of the main adjusting arrangement is transferred into the completely open position, is arranged in the same manner, necessarily enlarging the drive as in the document EP 1 725 795 B1.
The two known drives described above have a control head or a control unit, which is enclosed preferably by a separate housing, on the face side facing away from the valve housing of the double seat valve. This arrangement of the control unit requires an elongation of the first adjusting rod into the control unit, if there is to be position sensing of the independently driven first closing element. A position sensing of the dependently driven second closing element is not possible in a control unit arranged in this regard. In addition to the disadvantage of elongating the first adjusting rod into the control unit, there is the further disadvantage that a thusly arranged control unit enlarges the axial construction length of the double seat valve and the drive thereof.
Even with non-generic drives for double seat valves capable of seat cleaning found in the prior art, there is always the above described disadvantageous arrangement of the control unit. For example, the document DE 31 33 273 A1 discloses a so-called modularly built drive for a double seat valve which below the main adjusting arrangement for generating the closed and fully open position of the two closing elements, has two independently drivable individual adjusting arrangements for generating respectively a partially open position for each closing element, wherein the two individual adjusting arrangements together form a separate unit. Position indicating arrangements for the independently driven closing element are arranged in a separate housing on the face side of the main adjusting arrangement facing away from a valve housing. Furthermore, the pressure medium for pressurizing the main adjusting arrangement passes in relatively complex manner through a connection on the housing of the position indicating arrangement and then on the path via the adjusting rod into the main adjusting arrangement.
The document DE 40 14 474 C1 describes a drive, called a control head, for a disk valve, wherein there are two contactless signal transmitters spaced one above the other, above the control head in a cap resting on the latter, that report the closed or open position of the valve disk with the correspondingly displaced valve disk rod.
The document WO 02/093 058 A1 discloses a device for controlling the switching movement of a valve having at least one valve rod or adjusting rod translationally moved, supporting a closing element. The at least one valve rod, on one side of a valve housing, is guided out of the latter and guided into a drive pressurized with pressure medium, in which there is a main adjusting arrangement for generating the closed and fully open position of the valve and, if the valve is a double seat valve capable of seat cleaning, there are two individually controllable individual adjusting elements for generating in each case a partially open position for each closing element. In terms of control technology, the individual adjusting arrangements controls are interlocked so that only one closing element can take on a seat cleaning position. Here, the individual adjusting arrangements in addition to the main adjusting arrangement can be an integral component of the drive (so-called integral drive) or they supplement the main adjusting arrangement, either individually or together, in a modular design (modularly built drive). A control head is arranged on the face side of the valve housing facing away from the drive, which in a separate housing accepts at least one pilot valve for controlling the pressure medium, and additionally a position indicator that is connected to the valve rod of the independently actuatable closing element, and that detects the present position of the valve rod forming the valve rod movement, and delivers the present position indication of the valve rod in this respect, and accommodates means of control logic. The pilot valves are preferably electromagnetically actuatable auxiliary valves.
The document DE 10 2006 039 493 A1 discloses a double sealing valve with a so-called integrated drive unit which can bring the two independently movable closing elements from a closed position into a fully open position, and moreover each closing element selectively into a partially open position, wherein the partially open positions are interlocked in a manner described above. A control unit arranged on the face side of the drive unit facing away from a valve housing is formed such that within the control unit the position of both closing elements can be detected separately from each other. For this purpose, the adjusting rod, designed as a hollow rod, of the first (upper) closing element, and the adjusting rod, arranged therein, of the second (lower) closing element, are guided up into the control unit, where the respective position is detected by a plurality of assigned sensors. There is no information given in the document about the arrangement of pilot valves for controlling the pressure medium pressurizing the pressure medium chambers, however, it must be assumed that in this regard the pilot valves, for example, formed as electromagnetically actuatable auxiliary valves, are housed in the control unit, if the pressure medium for the pressure medium chamber to be controlled is not guided from the surrounding area to each of the valves, and is controlled by an externally arranged control.
Moreover, an arrangement for controlling pressure medium for a drive of a valve is known from the document DE 35 01 739 C1 which has a separate housing, which is arranged on the face side of the drive, not described in greater detail, facing away from a valve housing. In addition to an indicated position indicating device for the valve rod, a distributor piece is provided in the housing, that can control the pressure medium distribution necessary for standard and special functions of a valve if suitable auxiliary valves (pilot valves) are assigned to the distributor piece at various connections thereof.
The document DE 196 42 181 A1 discloses a control head for valves with a pneumatic drive for the food and beverage industry which is located in the same position to the drive as in the above-mentioned documents, and accommodates in the independent housing thereof means for connecting and distributing pneumatic lines, a solenoid valve or plurality of solenoid valves, possibly sensors for monitoring the position of the armature, and components of a control circuit. The valves at issue are pipeline switches in the broadest sense, the closing elements of which perform a pivot or stroke movement.
All of the drives described briefly above in conjunction with a valve and a control unit or control head, which describe the present state of the art of drives for valves, in particular double seat valves of process technology, particularly in the field of food and beverage industry, chemical, pharmaceutical and biotechnology, have in common the fact that the overall construction height or length of all these components results in the most unfavorable case from an addition of these lined up components. In general, the resulting total length is even greater because an obligatory so-called lantern housing with drainage function must be arranged between the valve housing and the drive so that in the event of leakages at the valve housing and/or at the drive, no contamination or mixing can occur between hostile fluids, the pressure medium in the drive and a product in the valve housing.
Large structural dimensions in process plants with a variety of valves require corresponding construction spaces that are not available in many cases, or the provision thereof causes corresponding costs. The efforts so far, to build the components of lantern, drive and control unit compactly and in a space-saving manner, at least in the direction of the required sequence thereof, i.e., in the axial direction of the drive, are insufficient.
It is an object of the present invention to further develop a generic drive for switching a double seat valve, so that this drive for actuating a double seat valve having a closing element (first configuration of the drive) formed as a slide piston and a closing element formed as a seat plate, or having two closing elements formed as seat plates (second configuration of the drive), are equally suitable and in the design thereof are simplified with respect to the construction known from the prior art. In addition, a further object of the invention is to simplify the aggregation of the drive and control unit in the design thereof and to significantly reduce the construction height of the aggregation, as measured in the axial extension direction of the aggregation compared in this respect to that known from the prior art.